Using Data Libraries

You can use the LIBNAME statement or function to assign librefs and engines to one or more folders, including the working folder. The examples in this section use the LIBNAME statement. For information about the LIBNAME function, see SAS Functions and CALL Routines: Reference.

The LIBNAME statement has the following basic syntax:

An explanation of all the arguments in this statement can be found in SAS Statements: Reference.

If you have SAS 9.3 data sets stored in the C:\MYSASDIR folder, you can submit the following LIBNAME statement to assign the libref TEST to that folder:

libname test V9 'c:\mysasdir';

This statement indicates that the libref TEST accesses SAS 9.3 files stored in the folder C:\MYSASDIR. Remember that the engine specification is optional.

The current working folder is shown in the status bar of the main SAS window. If you want to assign the libref MYCURR to your current SAS working folder, use the following LIBNAME statement:

libname mycurr '.';

If you have SAS files located in multiple folders, you can treat these folders as a single SAS library by specifying a single libref and concatenating the folder locations, as in the following example:

libname income ('c:\revenue' 'd:\costs');

This statement indicates that the two folders, C:\REVENUE and D:\COSTS, are to be treated as a single SAS library. When you concatenate SAS libraries, SAS uses a protocol for accessing the libraries, depending on whether you are accessing the libraries for read, write, or update.

You can concatenate multiple libraries by specifying only their librefs, as in the following example:

libname sales (income revenue);

This statement indicates that two libraries that are identified by librefs INCOME and REVENUE are treated as a single SAS library whose libref is SALES.

For more information, see Understanding How Multi-Folder SAS Libraries Are Accessed.

If you want to use another access method, or engine, instead of the V9 engine, you can specify another engine name in the LIBNAME statement. For example, if you want to access only Version 6.12 SAS data sets from your SAS 9.3 session, you can specify the V612 engine in the LIBNAME statement, as in the following example:

libname oldlib V612 'c:\sas612';

Another example is if you plan to share SAS files between SAS 9.3 under Windows and Version 6 under Windows, use the V6 engine when assigning a libref to the SAS library. Here is an example of specifying the V6 engine in a LIBNAME statement:

libname lib6 V6 'c:\sas6';

Remember that while SAS 9.3 can read Version 6 SAS data sets, Release 6 cannot read SAS 9.3 data sets. For methods of regressing a SAS 9.3 data set to a version 6 data set, see information in the Migration focus area at http:\\support.sas.com\migration\planning\files\regression.html.

For more information about using engine names in the LIBNAME statement, see Using SAS Files from Other Versions with SAS 9.3 for Windows and Reading BMDP, OSIRIS, and SPSS Files. You can also see the LIBNAME statement in SAS Statements: Reference.

Instead of assigning the same librefs each time you start SAS, you can specify a libref each time that SAS starts. In the New Library dialog box, select Enable at startup. The libref is available as soon as SAS initializes. Libraries that are enabled at start up are stored in the SAS Registry under the entry [CORE\OPTIONS\LIBNAMES].

If a folder contains SAS files that were created by several engines, only those SAS files that were created with the V6 engine that is assigned to the given libref can be accessed by using that libref. SAS files created with the V7, V8, and V9 engines can all access each other, but those engines cannot access files created with the V6 engine. You must specify the V6 engine to see those files. You can assign multiple librefs with different engines to a folder. For example, the following statements are valid:

libname one V6 'c:\mydir';
libname two V9 'c:\mydir';

Data sets that are referenced by the libref ONE are created and accessed using the compatibility engine (V8), whereas data sets that are referenced by the libref TWO are created and accessed using the default engine (V9). You can also have multiple librefs (using the same engine) for the same SAS library. For example, the following two LIBNAME statements assign the librefs MYLIB and INLIB (both using the V9 engine) to the same SAS library:

libname mylib V9 'c:\mydir\datasets';
libname inlib V9 'c:\mydir\datasets';

Because the engine names and the Windows pathnames are the same, the librefs MYLIB and INLIB are identical and can be used interchangeably.

You can also assign a libref using environment variables instead of the LIBNAME statement or function. An environment variable equates one string to another within the Windows environment. SAS recognizes two types of environment variables:

When you use a libref in a SAS statement, SAS resolves libref assignments in this order:

For example, if the Windows environment variable TEMP is assigned to C:\WINNT\TEMP and you use the following LIBNAME statement:

libname temp c:\public

the LIBNAME resolves to c:\public.

There are two ways of defining an environment variable to SAS:

The availability of environment variables makes it simple to assign resources to SAS before invocation.

You can use the SET system option to define a SAS environment variable. For example, if you store your permanent SAS data sets in the C:\SAS\MYSASDATA folder, you can use the following SET option in the SAS command when you start SAS or in your SAS configuration file to assign the environment variable TEST to this SAS library:

-set test c:\sas\mysasdata

When you assign an environment variable, SAS does not resolve the environment reference until the environment variable name is actually used. For example, if the TEST environment variable is defined in your SAS configuration file, the environment variable TEST is not resolved until it is referenced by SAS. Therefore, if you make a mistake in your SET option specification, such as misspelling a folder name, you do not receive an error message until you use the environment variable in a SAS statement.

Because Windows filenames can contain spaces or single quotation marks as part of their names, you should enclose the name of the physical path in double quotation marks when specifying the SET option. If you use the SET option in an OPTIONS statement, you must use quotation marks around the filename. For complete syntax of the SET system option, see SET System Option: Windows.

Any environment variable name that you use as a value for a system option in your SAS configuration file must be defined as an environment variable before it is used. For example, the following SET option must appear before the SASUSER option that uses the environment variable TEST:

-set test "d:\mysasdir"
-sasuser "!test"

In the following example, environment variables are used with concatenated libraries:

-set dir1 "c:\sas\base\sashelp"
-set dir2 "d:\sas\stat\sashelp"
-sashelp (!dir1 !dir2)

Note that when you reference environment variables in your SAS configuration file or in a LIBNAME statement in your SAS programs, you must precede the environment variable name with an exclamation point (!).

It is recommended that you use the SET system option in your SAS configuration file if you invoke SAS through a Windows shortcut.

You can execute a Windows SET command before invoking SAS to create a Windows environment variable. You must define the environment variable before invoking SAS; you cannot define environment variables for SAS use from a Command Prompt window from within a SAS session.

SAS can recognize environment variables only if they have been assigned in the same context that invokes the SAS session. You must define the environment variable in the Windows AUTOEXEC.BAT file that runs when Windows starts (thus creating a global variable), or define the variable in either a Command Prompt window from which you then start SAS or from the System Properties dialog box.

If you define an environment variable in a Command Prompt window, and then start SAS from the Start menu (or with another shortcut), SAS will not recognize the environment variable.

The environment variables that you define with the SET command can be used later within SAS as librefs. In the following example, the Windows SET command is used to define the environment variables PERM and BUDGET:

SET PERM=C:\MYSASDIR
SET BUDGET=D:\SAS\BUDGET\DATA

If you are running SAS interactively, use the Explorer window to view the active librefs. The Explorer window lists all the librefs that are active for your current SAS session, along with the engine and the physical path for each libref. Any environment variables that you have defined as librefs are listed, provided you have used them in your SAS session. If you have defined an environment variable as a libref but have not used it yet in a SAS program, the Explorer window does not list it.

In any SAS session, you can use the LIBNAME command to invoke the LIBNAME window. The Explorer window lists the active libraries. Using the LIBNAME window, you can view the contents of all your libraries.

The following LIBNAME statement writes the active librefs to the SAS log:

libname _all_ list;

You can clear a libref by using one of the following methods:

SAS automatically clears the association between librefs and their respective libraries at the end of your job or session. If you want to associate the libref with a different SAS library during the current session, you do not have to end the session or clear the libref. SAS automatically reassigns the libref when you use it to name a new library.

To clear a libref by using the Explorer window:

For more information about using the Explorer window to manage libraries, see The Little SAS Book or the SAS Help and Documentation.

To clear a libref by using the LIBNAME window:

To clear a libref by using the LIBNAME statement, submit a LIBNAME statement using this syntax:

If you specify a libref, only that libref is cleared. If you specify the keyword _all_, all the librefs that you have assigned during your current SAS session are cleared. (Maps, Sasuser, Sashelp, and Work remain assigned.)

To clear a libref by using the LIBNAME function, the only argument to the function is the libref:

libname(libref);

When you use the concatenation feature to specify more than one physical folder for a libref, SAS uses the following protocol for determining which folder is accessed:

The protocol illustrated by the following examples applies to all SAS statements and procedures that access SAS files, such as the DATA, UPDATE, and MODIFY statements in the DATA step and the SQL and APPEND procedures.

When a SAS file is accessed for input or update, the first SAS file found by that name is the one that is accessed. For example, if you submit the following statements and the file OLD.SPECIES exists in both folders, the one in the C:\MYSASDIR folder is printed:

libname old ('c:\mysasdir','d:\saslib');
proc print data=old.species;
run;

The same would be true if you opened OLD.SPECIES for update with the FSEDIT procedure.

If the data set is accessed for output, it is always written to the first folder, provided that the folder exists. If the folder does not exist, an error message is displayed. For example, if you submit the following statements, SAS writes the OLD.SPECIES data set to the first folder (C:\MYSASDIR), replacing any existing data set with the same name:

libname old ('c:\mysasdir','d:\saslib');
data old.species;
   x=1;
   y=2;
run;

If a copy of the OLD.SPECIES data set exists in the second folder, it is not replaced.

One possibly confusing case involving the access protocols for SAS files occurs when you use the DATA and SET statements to access data sets with the same name. For example, suppose you submit the following statements and TEST.SPECIES originally exists only in the second folder, D:\MYSASDIR:

libname test ('c:\sas','d:\mysasdir');
data test.species;
   set test.species;
   if value1='y' then
      value2=3;
run;

In this case, the DATA statement opens TEST.SPECIES for output according to the output rules. That is, SAS opens a data set in the first of the concatenated libraries (C:\SAS). The SET statement opens the existing TEST.SPECIES data set in the second (D:\MYSASDIR) folder, according to the input rules. Therefore, the original TEST.SPECIES data set is not updated; rather, two TEST.SPECIES data sets exist, one in each folder.

The Work data library is the storage place for temporary SAS files. By default under Windows, the Work data library is created as a subfolder of !TEMP\SAS Temporary Files folder. This subfolder is named _TDnnnnnnnnnn, as discussed in Work Data Library . Temporary SAS files are available only for the duration of the SAS session in which they are created. At the end of that session, they are deleted automatically. If SAS terminates abnormally, you might need to delete the temporary files.

By default, any file that is not assigned a two-level name is automatically considered to be a temporary file. A special libref of Work is automatically assigned to any temporary SAS data sets created. For example, if you run the following SAS DATA step to create the data set Sports, a temporary data set named Work.Sports is created:

data sports;
   input @1 sport $10. @12 event $20.;
   datalines;
volleyball co-recreational
swimming   100-meter freestyle
soccer     team
;

If you display the Explorer window now, you will see the Sports data set in the Work folder.

You can display all the temporary data sets that are created during this session from:

The Work data library is always associated with the V9 engine. You cannot change the engine associated with the Work data library. If you try to assign another engine to this data library, you receive an error message. Therefore, even if you have set the ENGINE system option to a different engine, any SAS files that are created in the Work data library are SAS 9.3 files.

You can use an environment variable in your Work data library specification, similar to the method illustrated earlier with the SASUSER system option. Use this technique when you do not want to use the default location for your Work data library. You can put something similar to the following in your SAS configuration file to set up an environment variable to use for your Work data library:

-set myvar c:\ tempdir
-work !myvar

The SET option associates the MYVAR environment variable with the C:\TEMPDIR folder. Then the WORK option tells SAS to use that folder for the Work data library. When you exit your SAS session, the temporary folders and any files that they contain are removed.

Although by default SAS files with one-level names are temporary and are deleted at the end of your SAS session, you can use the User libref to cause SAS files with one-level names to be stored in a permanent SAS library. For example, the following statement causes all SAS files with one-level names to be permanently stored in the C:\MYSASDIR folder:

libname user 'c:\mysasdir';

When you set the User libref to a folder as in the previous example and you want to create or access a temporary data set, you must specify a two-level name for the data set, with Work as the libref.

Alternatively, you can assign the User libref when you invoke SAS by using the USER system option or by creating a Windows environment variable named USER. If you have a Windows environment variable named USER, the USER libref is automatically assigned when you invoke SAS. For more information about the USER system option, see USER System Option: Windows and SAS System Options: Reference.